In general, the direct current (hereinafter, referred to as "DC") voltage generator is required to operate an internal circuit in a semiconductor memory device. Many kinds of the DC voltage generators have consumed a constant amount of DC power in order to maintain a DC voltage level set in accordance with each of objects thereof. The power consumption is also continued even in a stand-by state. Most of the power consumption of the self-refresh mode mainly occurs by a constant DC power continuously consumed during a very long stand-by state in the self-refresh mode that is carried on for data retention, when compared with a normal read/write operation.
In a conventional DC voltage generating circuit shown in FIG. 1, a bias voltage through resistors R1 and R2 drives an NMOS transistor NMOS1 and a PMOS transistor PMOS1, to generate the constant DC voltage supplied through an output terminal of the DC voltage generating circuit. However, much of the electric power consumption in the conventional DC voltage generating circuit is brought about by its being constructed to always generate the DC voltage irrespective of the stand-by state in the self-refresh mode.